Computer hard drives are usually subjected to a “burn in” testing procedure conducted in an environmentally controlled test chamber. These chambers are designed to isolate the drive from vibrations while applying controlled temperature and humidity changes so that the drive manufacturer can obtain accurate test results.
Computer hard drives are also usually subjected to thermal testing or environmental conditioning testing during the design and prototyping phases of the manufacturing process. This testing, also known as “final verification” testing, is also typically conducted in large environmental test chambers. The manufacturer selects the humidity, test temperature, and airflow inside the test chamber so that it simulates the thermal stress range of conditions that the device under test is realistically expected to “see” in its useful life. Alternatively, the humidity, test temperature, and airflow may be selected to be some multiple of the worst expected conditions. These tests can provide a valuable tool to verify product quality and reliability.
To optimize test time during burn-in and during final verification testing, the disk drive should be heated or cooled at a defined rate until the specific desired test temperature is reached while applying specified humidity. Accordingly, it is important to maintain a specific airflow over the drive during this phase to ensure that temperature gradients within the drive are typical of the end use environment. The airflow through the test chamber must also be sufficient to ensure a consistent humidity and temperature variance throughout the chamber while dissipating the heat generated during the tests by the operating device (typically about thirty watts per a disk drive), but not at a level at which excessive localized cooling would fail to simulate the final operational environment of the devices under test.
Conventional environmental test chambers consist of one or two chambers. One chamber provides a controlled environmental space for the items under test (the “testing chamber”), and is designed to provide heat and cool large numbers of disk drives, typically about 120 drives at a time. There is generally no feedback control from the drives, the control of the overall chamber temperature being the preferred mode of operation. Accordingly, significant temperature variations can and do occur within the testing chamber, which result in different temperatures for drives at different locations. Another problem with conventional environmental test chambers is that all of the files in the chamber are heated/cooled together. Thus, these systems are inherently designed for batch processing.
The second “tester” chamber, if included, typically provides a space for the tester hardware (in single chamber devices, the tester hardware is simply left out in the ambient air). The divider between the testing and tester chambers has customarily been a solid metal wall, with insulated electrical or other “as-needed” connections made via permanent holes in the wall. This solid metal wall severely limits the flexibility of applications and makes any alteration to accommodate different applications a time consuming and expensive process. The solid metal wall also allows significant heat transfer between the two chambers.
The drives are typically held in a fixture or a carrier while they undergo the burn-in or final verification testing procedures. One problem with conventional fixtures or carriers is that they are prone to transferring mechanical vibrations to the drive under test. Conventional holders or fixtures also fail to provide good air circulation around the drive, contributing to thermal gradients of as much as thirty degrees Celsius. Both of these conditions are undesirable because they add noise to the test results and generally reduce the utility of the environmental test chamber.
Another problem with current carrier designs is that they lack “user friendliness.” These designs typically use a “swing type” or “barn door” latch that requires a large rotational motion to engage or disengage the point clamping site with the drive. These latching mechanisms also do not provide clear access to both ends of the drive when the latch is open. These problems can interfere with cable connection and arrangement.
Yet another problem with current carrier designs is that they are relatively expensive because they require a large amount of raw materials and a large number of parts. This problem is compounded because conventional carrier designs are custom designed for a single use. For example, carriers built to test 3.5″ disk drives could not be used with 2.5″ drives. These problems increase the manufacturing and assembly cost of the carrier. Lack of flexibility is also a problem in for users who need to test a variety of devices, such as small batch manufacturers and research facilities.
Ideally, an environmental testing chamber and carrier testing station should individually subject each device under test to its required environment, should allow for accurate and precise control of the environment, and should allow the devices under test to be loaded/unloaded individually for a continuous flow of products through the testing station. This ideal, however, must be weighed against its cost of implementation.
Clearly, there is a need for more flexible environmental test chamber and hard drive carrier capable of accommodating different applications. There is also a need for a simple and inexpensive hard drive carrier that reduces vibration and improves airflow around the drive. In addition, there is a need for a more user friendly hard drive carrier that simplifies clamping/unclamping and that provides clear access to the ends of the drive at all times.